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Then iSCSI SANs emerged, giving organizations an Ethernet alternative to the complex and costly Fibre Channel (FC) for SANs. This required yet another decision even for SAN customers: Fibre Channel for performance or Ethernet for price and simplicity?

But now, you no longer have to choose between protocols when buying storage. Multiprotocol storage systems -- also known as unified storage -- offer a combination of NAS, iSCSI and SAN for greater flexibility. And these multiprotocol storage systems have become common, even in systems built specifically for small- to medium-sized businesses (SMBs).

In this tutorial on multiprotocol storage for SMBs, learn about NAS and SAN protocols, Fibre Channel vs. iSCSI SANs, and multiprotocol data storage systems for SMBs.

The two major protocols used by network-attached storage for sharing files are Network File System (NFS) and Common Internet File System (CIFS) for Windows. NFS was developed for sharing files between Unix systems across a LAN and CIFS is widely used for Windows. Many NAS products support both, along with TCP-based HTTP and FTP. Still, a NAS system that supports NFS and CIFS generally isn't what we refer to when we talk about multiprotocol storage. When people talk about multiprotocol storage, they mean either NAS and one or both of the SAN protocols, or Fibre Channel and iSCSI in the same box.

Because NAS uses Ethernet connectivity, NAS devices are usually easier to configure and manage than FC SANs. That also makes NAS a good fit with iSCSI in multiprotocol systems for SMBs.

Because it is Ethernet-based, iSCSI is easier to manage by IT people who have experience with this ubiquitous protocol. iSCSI also works with standard Ethernet switches. Fibre Channel often requires at least one IT person with Fibre Channel expertise, and usually needs expensive Fibre Channel switches and adapters. Fibre Channel is more difficult to manage because many changes made to a FC network must be scheduled and performed offline while iSCSI changes can be made without disrupting applications.

Fibre Channel SANs have been considered better performers than iSCSI SANs for several reasons. Fibre Channel has supported higher bandwidth than iSCSI, and was developed specifically for storage while Ethernet is a networking protocol.

Both those factors are changing. While most iSCSI still runs at Gigabit Ethernet, 10 Gigabit Ethernet (10 GigE) technology is becoming common on networking gear and most -- if not all -- iSCSI SANs will likely support 10 GigE by the end of 2010. That would bring it ahead of Fibre Channel, which peaks at 8 Gbps today while most users are still at 4 gig.

Standards are also in the works for an enhanced Ethernet that does not drop packets, making it more suitable for storage traffic. Known as Converged Enhanced Ethernet or Data Center Ethernet, this new Ethernet is a building block for the emerging Fibre Channel over Ethernet (FCoE) protocol.

There are other types of SAN protocols, such as FICON (Fibre Connectivity), Fibre Channel Protocol (FCP), Fibre Channel over IP (FCIP), and Internet FCP (iFCP). However, these protocols are designed for high-end enterprise storage arrays and are not found in systems for SMBs.

While Fibre Channel remains the dominant protocol for SAN arrays, all major vendors now offer iSCSI connectivity with their Fibre Channel SANs, and some vendors have designed their storage systems from the ground up to handle Fibre Channel, iSCSI and NAS. Not all iSCSI SANs handle Fibre Channel, however. The two most popular iSCSI platforms, Dell Inc.'s EqualLogic and Hewlett-Packard (HP) Co.'s LeftHand Networks, are iSCSI-only.

Editor's Tip: For more information about SANs for SMBs devices, read our article on iSCSI SANs for SMBs.

NetApp, which began as a NAS vendor, pioneered multiprotocol systems by adding Fibre Channel and then iSCSI connectivity options to all of its arrays. NetApp's Data Ontap operating system supports NFS, CIFS, iSCSI and Fibre Channel.

NetApp's main rival EMC Corp. began as a Fibre Channel vendor, then added dedicated NAS boxes. EMC lagged NetApp by a few years in embracing unified storage systems but added iSCSI capability to its Celerra NAS platform in 2006. Today, EMC's Celerra Unified Storage Platform supports CIFS, NFS, FC, and iSCSI. EMC has also added iSCSI connectivity for its Clariion and Symmetrix FC SAN arrays.

NAS vendors such as BlueArc Corp., OnStor (now part of LSI) and Nimbus Data Systems Inc. have added iSCSI. SAN vendors 3PAR and Compellent Technologies also include iSCSI connectivity with Fibre Channel systems. Compellent also offers a NAS gateway built on Windows Server and 3PAR connects to third-party NAS vendors. GreenBytes Inc. came out of stealth in September with a NAS and iSCSI system.

Early multiprotocol systems involved attaching an iSCSI or NAS gateway to a FC SAN, but most multiprotocol systems now have native block and file protocols without the need for bridges or gateways. Protocol support is more tightly integrated in these systems, and don't require add-on GUIs or management tools.

While lower end versions of enterprise data storage systems can be used for smaller enterprises, medium-sized businesses and departments, other vendors have beefed up desktop NAS boxes with iSCSI support for SMBs. These include EMC Iomega StorCenter ix2 and ix4 systems, Buffalo Technologies TerraStation, and NetGear ReadyNAS.

Microsoft Corp. made it easier for its OEM partners to build unified storage systems for SMBs when it released Windows Storage Server 2008 in May. Windows Storage Server 2008 includes an integrated iSCSI target for building systems that support NAS and IP SANs. Previously, Microsoft offered Windows Storage Server 2003 for NAS and the Windows Unified Data Storage Server for iSCSI but Storage Server 2008 combines the two. HP's StorageWorks X1000 SMB system is built on Windows Storage Server 2008 with NAS and iSCSI capabilities.

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